Organ-specific reduction in the abundance of a mitochondrial protein accompanies fertility restoration in cytoplasmic male-sterile radish

Abstract

The mitochondrial DNA of plants containing the male sterility-causing Ogura cytoplasm of radish contain a novel gene, orf138, that is transcribed as part of a bicistronic mRNA. Genetic studies have previously linked male sterility with the orf138 locus. To determine if orf138 is expressed at the protein level, and investigate the effect of fertility restoration on ORF138 levels, we have raised antibodies to an ORF138-glutathione S-transferase fusion protein. Anti-ORF138 antibodies detect a 20 kDa protein that is associated with the mitochondrial membrane of sterile Ogura radish plants. Nuclear restoration is accompanied by a dramatic reduction in the amount of this protein in mitochondria of flowers and leaves, but not roots of fertile Ogura radish plants. The presence or absence of fertility restoration genes has no detectable effect on the size, abundance, or RNA editing patterns of orf138 transcripts. These results support genetic studies that have implicated orf138 in Ogura cytoplasmic male sterility and suggest that the restorer genes may be affecting either the translation or stability of ORF138.

Cell type-specific loss of atp6 RNA editing in cytoplasmic male sterile Sorghum bicolor

“…Most investigations on cms in higher plants are conducted with etiolated shoots or tissue cultures, with the exception of a few reports (31,32) that showed a cell type-specific effect of fertility restoration of a cms-related gene. Based on our data, it appears that cell-and tissue-specific effects in higher plants may be more common than previously believed.…”

Interactions of Mitochondrial and Nuclear Genes That Affect Male Gametophyte Development

“…The fertile revertant cybrids also lacked the 19-kD ORF138 protein detected in sterile lines (Grelon et al, 1994). The ORF138 protein product also is reduced greatly in fertility-restored lines containing Rfo (Grelon et al, 1994;Krishnasamy and Makaroff, 1994;Bellaoui et al, 1999); however, no difference in the orf138 transcript profile was detected in fertile versus CMS plants (Krishnasamy and Makaroff, 1993;Bellaoui et al, 1999). When the region homologous with orf138/atp8 in Kosena radish was sequenced, a gene highly similar to orf138 was detected next to atp8.…”

The Rf and Rf-like PPR in higher plants, a fast-evolving subclass of PPR genes

“…33 Molecular events associated with fertility restoration do not impact the size or the abundance of the orf138 mRNA, even in a tissue-specific manner. 31,33,34 Additional analyses showed Finally, a number of as-yet-unidentified restorer genes are strongly suspected to encode PPR proteins since preliminary analyses indicate that they map to chromosomal regions containing one or several Rf-like PPR genes. This includes a second restorer gene (Rf2) of the sorghum A1 CMS, which was resolved to a 236 kb region.…”